Antistall technology (AST) is a mechanical downhole solution that aims to adjust the drilling torque automatically in real time. Originally, the tool was developed by Tomax AS for coiled-tubing applications where it has proven its ability to successfully reduce vibrations, motor stalls, equipment failures, and general wear, in addition to increasing the penetration rate and run length (Dagestad et al. 2006). The tool was then developed further based on the need for a similar solution for rotary drilling. The goal was to eliminate cutter-induced torque variations and string stalls in difficult formations and resultant harmful effects. Prototype AST tools were made in sizes ranging from 6¾ to 8¼ in. The tools were then run in test wells and later in field operations with a variety of tool configurations until the database, in addition to two controlled trials, counted 25 regular jobs-mainly on the Norwegian Continental Shelf. The paper describes in detail, both based on theory and on field experience, how the bit-induced torque fluctuations are significantly decreased to improve penetration, and how bottomhole-assembly (BHA) damage is prevented to increase run lengths.
Anti Stall Technology (AST) is a mechanical downhole solution which aims to adjust the drilling torque automatically in real time. Originally, the tool was developed by Tomax AS for coiled tubing applications where it has proven its ability to successfully reduce vibrations, motor stalls, equipment failures and general wear, in addition to increasing the penetration rate and run length (Dagestad, V 2006). The tool was then developed further based on the need for a similar solution for rotary drilling. The goal was to eliminate cutter-induced torque variations and string stalls in difficult formations and resultant harmful effects. Prototype AST tools were made in sizes ranging from 6 ¾" to 8 ¼". The tools were then run in test wells and later in field operations with a variety of tool configurations until the database, in addition to two controlled trials, counted 25 regular jobs -mainly on the Norwegian Continental Shelf. The paper describes in detail, both based on theory and on field experience, how the bit-induced torque fluctuations are significantly decreased to improve penetration, and how BHA damage is prevented in order to increase run lengths.
fax 01-972-952-9435. AbstractSince their introduction in 1997, rotary steerable drilling systems have delivered significant gains in drilling efficiency. In addition to this fundamental benefit, these systems have enabled more challenging wells to be drilled at low risk with a wide range of other advantages, including improved well placement, etc.Continuous rotary drilling operations do however bring with them certain challenges which must be considered before rotary steering is selected for use. These include instantaneous penetration rate, specifications of rig rotary equipment, casing or drillpipe wear, stress on the drillstring, loss of drilling power through wellbore friction and drilling dynamics.Using high powered drilling motors, traditional performance drilling has been applied since the early 1990's to improve penetration rates by applying high power and consistent operating parameters directly to the drillbit. This has however been limited to straight holes or the most basic of directional profiles.A system has been developed which integrates a specially designed high power drilling motor within a high speed rotary steering assembly. By using this new system: • many of the challenges of continuous rotary drilling are mitigated, • more complex wells benefit from the advantages of traditional performance drilling, • existing drilling envelopes can be extended to further improve field recovery. This paper discusses the engineering design of the complete system, including the specially designed motor and high speed rotary steering system. The paper then goes on to discuss specific applications where the system should be considered for use, illustrated with results from real examples.
The Integrated Under-Reamer (IUR) was developed in 2007 in a joint project between an Operator and Service company. The tool was designed to allow for unlimited opening and closing of the tool to provide selective hole opening in unstable formations e.g. unstable shale or swelling salt. Furthermore the tool should be able to close for pull out of hole (POOH) while keeping the circulation continuously on. To accommodate for this the tool was designed to be fully integrated into the modular bus structure of the downhole BHA. Electronics were developed to activate and deactivate the tool from downlink commands sent downhole and distributed via the communication bus to the IUR. Sensors in the IUR detect the status of the tool: such as position of the cutter blades and the health of the tool. This data is transmitted to surface using the MWD pulser. The data is displayed in real-time for immediate review by the drilling team. Additional diagnostic data are stored in memory for post run analysis. Advanced autonomous fail safe control was designed to make sure the tool can always be closed either by downlink or other procedures to allow unrestricted pulling out into smaller hole or the casing shoe. In the case of communication problems a procedure is available for back-reaming with automatically closing the blades. A case history is presented where a water injection well needed increased clearance to run 6 5/8" completion screens. Using the IUR, the well was opened up while drilling from a 8 ½" pilot hole to 9.05". The IUR was de-activated and re-activated successfully several times during drilling the section. The operational procedure is described, and caliper data are presented. The well was completed on plan. At the end an outlook will be given on future reaming on demand applications.
In liner drilling operations, the annular velocity of the drilling fluid drops significantly when it transits from the narrow cross section of the openhole-liner annulus into the increased annular volume between the casing and the drillpipe. The reduced annular velocity above the liner can cause critical hole cleaning problems that can jeopardize the entire drilling operation and, therefore, must be managed. To effectively mitigate this problem, a major operator and service company jointly developed and tested a smart flow diverter that can be positioned in the drillstring directly above the liner running tool. The flow diverter (FLD) is designed as a standalone tool that can be placed anywhere in the drillstring and is independent of the measurement-while-drilling (MWD) service-supplier. It can be used in different applications, e.g. under-reaming operations and liners without tieback, where enhanced, continuous hole cleaning is required. The fluid bypass of the flow diverter is simply activated either by drillstring rotation and flow or by a flow pattern signal if string rotation is not possible. These surface manipulations are recognized and interpreted by the flow diverter sensors and electronics. The concept enables an unlimited amount of activations and both activation principles can be incorporated into standard connection procedures, thereby eliminating nonproductive time (NPT). The FLD went through extensive testing and was run in steerable drilling liner and in other applications. The paper presents the features and activation principle of the technology, its benefits and field experience in combination with steerable drilling liner (SDL) technology and how the utilization of the technology in an underreamer application resulted in an optimized bottomhole assembly (BHA) design preventing previously experienced formation washouts.
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